A family of four lives in a scroungy basement in an unnamed South Korean city. They’re shown huddling in the bathroom to steal the Wi-Fi signal from a local coffee shop, seeking out a living by folding pizza boxes. Perhaps the most memorable moment comes when they hear a fumigator spraying the neighborhood, and the father stops his son from closing the windows: “Let them, it’s free pest removal.” They continue eating dinner while coughing from the fumes. It’s a quintessentially Bong Joon-Ho movie, and it’s one of many fantastic touches in “Parasite,” his latest film and one of the year’s best.

For the Kim family, things begin looking up when eldest son Ki-woo (Choi Woo-sik) gets a tip from a friend about a job teaching English. The fact that he doesn’t have a college degree is irrelevant, and some quick forgery later, he arrives at the swank modernist house of the Parks: naive but elegant mother Yeon-kyo (Jo Yeo-jeong), undefined businessman Dong-ik (Lee Sung-kyun), teenage daughter and pupil Da-hye (Jung Ji-so) and troubled youngest child Da-song (Jung Hyun-jun), pointedly obsessed with Native American aesthetics. It is this last child where Ki-woo puts his plan into action: one small suggestion later and his sister Ki-jung (Park So-dam) is Da-song’s art teacher/therapist (when asked about her skill by her family, she replies “I just googled art-therapy, then ad-libbed the rest”). Soon Ki-woo’s mother Chung-sook (Jang Hye-jin) is employed as the housekeeper and his father Ki-taek (frequent Bong collaborator Song Kang-ho) is the driver. One thinks they know where this is going. It’s just when you think you’ve figured things out that Bong pulls the rug out from underneath you, and the plot begins its series of twists and turns.

The greatest pleasures of “Parasite” are in these surprises, so in the interest of preserving things, I won’t divulge any more. What I will say is that “Parasite” is a rollicking piece of entertainment blended with a potent metaphor about class struggles and rage. No surprise, given that Bong also directed the excellent blockbuster “Snowpiercer,” which puts its metaphor on a very literal runaway train. He’s at the height of his very considerable powers, expertly working his signature blend of black comedy with tonal shifts that would be jarring if anyone else was behind it. The best example of this is a powerhouse sequence in the middle, rapidly switching between farce and suspense on a dime and succeeding at both. It’s this tight control of tone that makes everything in the script work.

At the center of it all is the theme of class. Bong resists making it an easy us versus them metaphor (something already done in Snowpiercer). The Parks’ crime isn’t so much cruelty as it is obliviousness. They’re so privileged that they simply don’t about things that the Kims constantly worry about. The Kims, meanwhile, are the ones we identify the most with, but they’re scamming their way through a family that really hasn’t done anything but live their lives. It’s not a call to action so much as an observation of the way things are; the lower classes will always fight each other for a chance at the uppers while the upper classes barely even notice the lowers exist unless they need something. These metaphors are baked into the script and the nice house that serves as the center.

Ever since it won the Palme d’Or in a unanimous decision, “Parasite” has been the most anticipated film for many. It lives up the hype, being equal parts horrifying and gut-bustingly funny, often at the same time. The greatest joy is just wondering where the story is going to go next as it builds to a devastating finale on par with Bong’s “Mother” for dread. More than anything, “Parasite” is a pleasure to watch, a thing of careful construction perfectly executed.